1,2-Dihydropyridine compounds possess antagonistic action against AMPA receptor and/or inhibitory action against kainate receptor and are useful as therapeutic or prophylactic agents for neurodegenerative diseases and others. Particularly, 3-(2-cyanophenyl)-5-(2-pyridyl)-1-phenyl-1,2-dihydropyridin-2-one (hereafter referred to as compound (1)) shows significant antagonistic action against AMPA receptor (see Patent Document 1).
Although Example 7 in Patent Document 1 discloses a process for producing the compound (1), there is merely described, “the residue is purified by silica gel column chromatography (ethyl acetate/hexane-1:2)” and there is no disclosure of the form of the obtained compound.    [Patent Document 1] WO/JP01/96308